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Large temporal and spatial variability in soil nitrogen (N) availability leads many farmers across the United States to over-apply N fertilizers in maize (Zea Mays L.) production environments, often resulting in large environmental N losses. Static Stanford-type N recommendation tools are typically promoted in the United States, but new dynamic model-based decision tools allow for highly adaptive N recommendations that account for specific production environments and conditions. This study compares the Corn N Calculator (CNC), a static N recommendation tool for New York, to Adapt-N, a dynamic simulation tool that combines soil, crop, and management information with real-time weather data to estimate optimum N application rates for maize. The efficiency of the two tools in predicting the Economically Optimum N Rate (EONR) is compared using field data from 14 multiple N-rate trials conducted in New York during the years 2011 through 2015. The CNC tool was used with both realistic grower-estimated potential yields and those extracted from the CNC default database, which were found to be unrealistically low when compared with field data. By accounting for weather and site-specific conditions, the Adapt-N tool was found to increase the farmer profits and significantly improve the prediction of the EONR (RMSE = 34 kg ha⁻¹). Furthermore, using a dynamic instead of a static approach led to reduced N application rates, which in turn resulted in substantially lower simulated environmental N losses. This study shows that better N management through a dynamic decision tool such as Adapt-N can help reduce environmental impacts while sustaining farm economic viability.

Arbuscular mycorrhizal (AM) fungi (phylum Glomeromycota) are important components of natural and managed ecosystems. We explored the AM fungal assemblage in a selection of maize fields across a landscape in eastern New York State and characterized their diversity, dominance, and species abundance distribution. In this managed agroecosystem, we could investigate environment-influenced composition and diversity patterns unencumbered by immediate host species effects. We found that AM fungal taxon abundances were distributed lognormally, which suggests that the fungal community structure is shaped in a complex manner by many interacting niche-related factors rather than by only a single factor of disturbance associated with agricultural management. In addition to species abundance distribution, the focal assemblage shared with natural AM fungal communities a pattern of very strong dominance of certain taxa. To quantify this pattern, we developed two new indices “overdominance” and “inequitability”. Contrary to expectations based on observations of natural AM fungal communities, we found that most of the individual field communities were dominated by taxa from within a narrow phylogenetic range. At the landscape scale, we did not find an inverse relationship between the levels of taxonomic richness and phylogenetic relatedness expected in complex communities shaped by competitive exclusion.

The arbuscular mycorrhizal (AM) fungi (phylum Glomeromycota) are important for the functioning of terrestrial ecosystems because of their influence on plant nutrient relations and plant responses to stress. To assess the impact of dispersal limitation and identify niche-related environmental gradients affecting AM fungal community composition and structure, we studied AM fungal communities in an assemblage of maize fields across an eastern New York State landscape. We expressed AM fungal community differences in terms of abundance structure (Bray–Curtis dissimilarities), the presence of unique phylogenetic lineages (UniFrac), and mean phylogenetic relatedness between samples (mean patristic distance, MPD). We did not find strong evidence of dispersal limitation or isolation by distance within or between field sites. To identify environmental factors that may be related to community differentiation, we projected vectors of edaphic variables onto nonmetric multidimensional scaling (NMDS) ordinations of community dissimilarity measures. Of these factors, soil textural components appeared most strongly related to AM fungal community differences. We speculate that this pattern may be explained by the relationship between texture and soil moisture availability. In addition to soil textural components, phylogenetic measures of community differentiation suggested that AM fungal community structure was affected by nutrient concentrations, particularly Mg. Of the two phylogenetic indices of community differentiation, MPD was more consistent and stable with our data, whereas the UniFrac metric failed to be interpretable in several cases. Overall, our data suggest that, rather than phosphorus or pH, soil texture may have an influence on AM fungal community structure over large agroecological scales.

Rising concerns about greenhouse gases, increased fuel prices, and the potential for new high value agricultural products have raised interest in the use of maize stover for bioenergy production. However, residue harvest must be weighed against potential negative impacts on soil quality. This study, conducted in Chazy, NY, evaluated the long-term effects of 32 yr of maize (Zea mays L.) stover harvest vs. stover return on soil quality in the surface layer (5-66 mm) under plow till (PT) and no-till (NT) systems on a Raynham silt loam (coarse-silty, mixed, active, nonacid, mesic Aeric Epiaquept) using physical, chemical, and biological soil properties as soil quality indicators. Twenty-five soil properties were measured, including standard chemical soil tests, aggregate stability (WSA), bulk density, (ρ b ) penetration resistance (PR), saturated hydraulic conductivity (K s ), infiltrability (Infilt), several porosity indicators (aeration pores(PO > 1000), soil water potential = Ψ > -0.36 kPa; air-filled pores at field capacity (PO > 30), Ψ > -10kPa; available water capacity (AWC), -1500 < Ψ < -10 kPa), total organic matter (OM), parasitic (Nem Parasitic ) and beneficial nematode (Nem Beneficial ) populations, decomposition rate (Decomp), potentially mineralizable N (PMN) and easily extractable (EEG) and total glomalin (TG). Only eight indicators were adversely affected by stover harvest, and most of these effects were significant only under NT. Almost all indicators affected by stover removal were affected equally or more adversely by tillage. A total of 15 indicators were adversely affected by tillage. Results of this study suggest that, on a silt loam soil in a temperate climate, long-term stover harvest had lower adverse impacts on soil quality than long-term tillage. Stover harvest appears to be sustainable when practiced under NT management.